The extraction of crude oil from reservoirs involves formation of water in crude oil emulsions, crude oil in water emulsions and tertiary emulsions water/crude oil/water and crude oil/water/crude oil. Such emulsions are produced by the turbulence promoted by the pumping power used in wells. These emulsions can be very stable and their formation is favored and stabilized by compounds naturally present in crude oil such as clays, naphthenic acids, rusty hydrocarbon and asphaltene. The water emulsified in crude oil contains inorganic salts; mostly sodium, magnesium, calcium chlorides, carbonates and sulfates; and iron sulfides and oxides. If not removed, these salts may cause various problems of corrosion and scaling in all the subsequent refining process (piping, storage tanks, distillation columns, heat exchangers, catalysts, piping systems, etc.). Additionally, the produced crude oil must comply with international quality standards relating to the maximum content of salt and water, for possible export [1].
Therefore, from an economic point of view, it is imperative and important to separate water from crude oil and simultaneously reduce the salt content.
Since the last century, different chemical products have been used to carry out the demulsification process of water in crude oil. The water is commonly added as formulations consisting of groundbreaking agents, coalescing and emulsion clarifiers. The nature of these products are polymeric.
Examples of polymeric formulations include alkoxylated alkylphenol resins formaldehyde [2], alkoxylated epoxy resins [2], block copolymers of polyoxyethylene-polyoxypropylene-polyoxyethylene (POE-POP-POE) and polyoxypropylene-polyoxyethylene-polyoxypropylene (POP-POE-POP), using various initiators such as propylene glycol or ethylenediamine [3], polyethers, polyesters and/or polyurethanes, polyesters together by dicarboxylic acids and/or diisocyanates [4], aliphatic and aromatic anhydrides in combination with glycolic esterified resins [5], ethyl cellulose on nano magnetic particles crosslinked in combination with the application of external magnetic fields [6], cationic surfactants [7], symmetric type surfactants with polyoxyethylene spacers fragments [8] among some others.
The Mexican Petroleum Institute (Research Program in Molecular Engineering) proposed innovative solutions to the problem of dehydrating and desalting of crude oils, resulting in four patent applications in this specific area. The formulations used triblock type copolymers poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) which were bifunctionalized with amines to dehydrate heavy crude oils, achieving water removal 30 to 80% and salts of heavy crude oils 30-65% [9-10]. Another method uses ionic liquids individually and formulations for dehydrating and desalting medium, heavy and extra heavy crude oils (API gravities between 8 and 20) where dehydrating and desalting efficiencies reached about 90% and 76%, 90% and 71%, 90% and 71%, respectively. The addition of additives was done in concentrations between 50 and 2000 ppm [11]. Another method involves the application of synergistic formulations of ionic liquids (IL's) and formulations of triblock copolymers (CF's) α,ω-bifunctionalized with amines of ethylene polyoxide-propylene polyoxide-ethylene polyoxide, each individually or in formulation, in crude oils whose gravities are between 9 and 30°API [12].